A compound turbo-molecular pump used in order to achieve a high vacuum environment in a vacuum device has a thread groove pump composed of a rotating cylinder and a fixed cylinder facing the rotating cylinder, the thread groove pump being provided downstream of an axial flow pump made by alternately disposing rotating blades and fixed blades.
In this thread groove pump, the smaller the gap is between the opposing rotating cylinder and fixed cylinder, the more the exhaust performance is improved, and high precision is therefore required in the rotating cylinder portion constituting the thread groove pump.
Therefore, the rotating cylinder portion is normally made of metal and is cut integrally with the rotating blades, but there have been proposals of replacing the rotating cylinder portion with an FRP (fiber-reinforced resin) cylinder that is lightweight and high in strength in order to reduce the weight of the rotating body having the rotating blades and the rotating cylinder (see Patent Documents 1 and 2, for example).